Unloading system for air-compressors.



0. R. WIKANDER.

UNLOADING SYSTEM FOR AIR COMPRESS ORS. APPLICATION FILED FEB. 18. 1914.

1,1091%, Patented Aug. 24-, 1915.

2 SHEETS-SHEET INVENTOR WITNESSES 0. R. WIKANDER.

UNLOADING SYSTEM FOR ME COMPRESSORS.

API LICATION FILED FEBv I8. 1914.

Patented Aug. 24, 1915.

gSHEETS-SHEET 2.

WITNESSES p? K ATTORNEYS OSCAR R. WIKANDER, OF PITTSBURGH, PENNSYLVANIA.

UNLGADING SYSTEM FOR AIB-CQMPRESSORS.

Application filed itebruary 18, 1914.

To all whom it may concern Be it known that I, OsoAR R. WIKANDER, acitizen of the United States, and resident of Pittsburgh, in the .countyof Allegheny and State of Pennsylvania, have invented a new and usefulImprovement in Unloading Systems for Air-Compressors; and I do hereby,declare the following to be a full, clear, and exact descriptionthereof.

My invention relates to regulating mechanism in connection with fluidcontrolling devices, such, for example, as air compressors, blowingengines, vacuum pumps, etc.

One of the objects thereof is to provide very sensitive and efficientregulation of the volume of intake fluid for such devices, so as to makeit correspond exactly and at all times to the amount of fluid consumed,thereby in one aspect of the invention maintaining the pressure in thereceiver or pipe system practically constant. At the same time, theinvention serves toreduce the active power required to operate theapparatus approximately in proportion to the amount of fluid beingoperated upon. This regulator operates in such a manner that, in casethe suction valves of an air compressor, for example, are used for thepurpose of regulation, the same are kept open by force during only apart of each discharge stroke and close as soon as the amount of intakeair remaining in the cylinder has decreased so as to correspond to theamount of compressed air consumed at the time being. The point ofclosing or of cut ofl of the suction valves is the same on everystrokeas long as the consumption of air remains constant, but varies withvarying air consumption so as to maintain a constant receiver pressure.

' If the discharge valves are used for the regulation they remain forcedopen during only a part of the following suction stroke, thusdistinguishing from'known construe tions, and close as soon as theamount of compressed air returned into the pump cylinder is so greatthat it, after expansion to intake pressure, will leave suficient roomfor fresh air to enter the cylinder, during the last part of the suctionstroke, to such an amount as to correspond to the Consumption ofcompressed air at the time being. The point of closing or cut off is thesame on every suction stroke as long as the consumption of air remainsconstant, but varies with Specification of Letters Patent.

- Patented Aug. $4, 31915.

serial No. 819,483.

varying consumption of compressed air so as to maintain a practicallyconstant receiver pressure.

Themethod, whereby the closing of the automatic valves at an adjustablepoint during the return flow of the air or gas is eflected, consistssimply in a very gradual regulation of the force holding said valvesopen against the pressure exerted by their springs. The return flow ofthe elastic fluid through the suction valves will, on account of thethrottling action of the latter, cause an increase of pressure in thecylinder tend ing to close said valves, and this pressure will efl'ectsuch closure when the piston has reached a point in its stroke, thelocation of which is dependent upon said throttling action. The lessintense this action, the more said point will advance toward the end ofthe stroke. (It should be said that the inventor uses the term strokehere to designate movement of the piston in one direction; or, a singlemovement of the piston from one end of the cylinder to the other.) Thereturn flow of the elastic fluid through the discharge valves will, onaccount of the throttling action of the latter, cause a decrease ofpressure in the cylinder, and this decrease will effect the closure ofsaid valves at a point in the stroke, the location of which advancestoward the end of the stroke in accordance with the decreasing intensityof said throttling action. The valves will close where this increase ordecrease of pres-- tended to cover the application of saidmethod to theregulation of the volume of an unyielding fluid, such as water, passingthrough a reciprocating pump. In the latter case, it is, however,necessary to regulate the suction as well as the discharge-valves if wedesire to cover the entire range of regulation from no load to fullcapacity. While the volume ordinarily 'will be regulated so as tomaintain a constant pressure in the discharge tank or pipe system, itshould be understood that said regulation can be controlled by otherfactors as well, such as speed or power-consumption of the prime mover.

In order to clearly illustrate the spirit of this invention, a fewapplications of same to special cases'will be described in detail.

Figure 1 represents an ordinary puppet valve air compressor, providedwith automatic volume regulation acting upon the suction valves so as tokeep the receiver pressure constant. Fig. 2 represents a piston inlettype of air compressor, provided with automatic volume regulation actingupon the discharge valves, so as to keep the receiver pressure constant,and an additional device so as to unload the air compressor completely,should the speed of the prime mover fall below a'certain limit.

Referring to Fig. 1, the piston 1 works in the cylinder 2 of a powerdriven air compressor. The suction valves 3 are provided with springs 4,which tend to close them, and with pistons 5 which are acted upon by theair pressure in the cylinder 6. These cylinders are connected by meansof a pipe 7 to the auxiliary tank 8. This tank communicates with theatmosphere through a leak 9 and with the main reservoir 10, through theopening 11, which is closed by means of the pilot valve 12 as soon asthe force of the adjustable spring 13 overcomes the air pressure of thereservoir 10 acting through thepipe 14 on the bottom of the valve piston15. An adjustable needle valve 16 can be arranged so as to obtain aconstant leak from the main to the auxiliary reservoir, therebypreventing the pressure in the latter from decreasing below a certainvalue. When the compressor is working at a constant partial load, thevalve 12 will allow some air to enter the auxiliary tank 8 through theopening 11 and the same quantity of air will escape through the leak 9,thereby keeping the pressure in the reservoir 8 and the pressure actingupon the pistons 5 in the cylinders 6, constant. The suction valves willclose at such a point of the discharge stroke as to compress exactly the-quantity of air consumed, the pressure in the main tank 10 remainingconstant.

A change in the consumption of air will cause a slight increase ordecrease of the pressure in the main tank 10 and the quantity of airentering the reservoir 8 through the opening 11 will increase ordecrease, thereby changing the pressure in said reservoir and the cutofl of the suction valves until new conditions of equal supply andconsumption of compressed air at a slightly increased or decreased tankpressure are established. A certain pressure in the auxiliary tank 8will balance the action of the valve springs to such an extent as tooppose a minimum of resistance to the intake air and at this pressurethe compressor will produce its maxithe compressor and only allowing theamount of intake air to vary with the consumption of compressed air aslong as the latter remains below said reduced capacity.

Referring to Fig. 2 the piston 17 works in the cylinder 18 of an aircompressor, said piston having inlet valve 19. The discharge valves 20which are preferably of cylindrical form, are provided with springs 21which tend to close them. These cylindrical valves are acted upon by theair pressure between the lower ends of said valves and the ends of theplungers 22 upon which the valves slide. Through holes 23 in saidplungers and through the pipe 7 these cylinder valves 20 are connectedto the auxiliary tank 8, and said tank communicates with the atmospherethrough the leak 9 and with the main reservoir through the opening 11which is controlled by the needle valve 24. This needle valve is mountedon the piston 25 which piston has an extension 26 extend ing into achamber 27 which chamber communicates with the atmosphere through anopening 27. Above the piston 25 is a second piston 29 having a headedstem or rod 30 which extends within a chamber31 of an adjusting screw 32adjustable in the piston casing 33. A spring 34 surrounding the stem 30normally has a tendency to raise the piston 29. The chamber 35 betweenthe piston 29 and the screw plug 32 communicates with the main pressuretank by a pipe 36.

Also the chamber 37 between the lower end of the piston 25 and the valveseat 11 communicates with the main pressure tank through a pipe 38having a regulating valve 39 therein. A needle point globe valve 41allows enough of the pressure air contained in the auxiliary tank toescapetothe atmosphere so as to unload the compressor by hand ifdesired. A similar needle point valve 42 can be bperated by means of aspeed regulator so la's to increase or decrease the pressure intheauxiliary reservoir 8, and the amount of intake air to the compressorin case of increase or? decrease in speed of the prime mover. Anincrease or decrease in speed of the latter is, as a rule, produced by adecrease or increase of the power consumption, and the latter factorcan, therefore, indirectly by the same means be used for the control ofthe amount of intake air to the compressor. 3 a

' When the compressor 1 is working at 'a constant partial load the airunder pressure from the main tank {will enter the chamber 35 through thepipe 36 and counteract the tendency of the spring 34: to raise thepiston 29, said piston will therefore bear upon the extension 26 of thepiston 25 carrying the needle valve 24 against the pressure entering thechamber 37 through the pipe 38 to such an extent that the air will enterthe auxiliary chamber 8 through the passage 11 at the same rate as itescapes through the leak 9 thereby keeping constant the pressure in thereservoir 8 which through the pipe 7 and opening 23 acts upon thecylindrical valve 20. Under these conditions the pressure in theauxiliary chamber 8 will be somewhat less than that in .the main tankand in the passage 40 leading from the cylinder 18'to said main-tank.Owing to this low pressure thus created in the plungers 22 the dischargevalves will'be kept open during part of the following suction stroke,and allow a certain amount of compressed air to reenter the cylinderfrom the outlet passage 40 and expand in'the cylinder to intakepressure. During the remaining part of the suction stroke, the amount offresh air drawn into the cylinder will exactly correspond to theconsumption of compressed air at the time being and the air pressure inthe main tank will remain constant. Assuming now that the consumption ofcompressed ,air is increased, a slight drop of pressure in the main tankwill result and the spring 34 will over come the eflect of the tankpressure on the piston 29 and will allow said piston to rise therebypermitting the piston 25 carrying the needle valve 24 to rise andpermitting a greater quantity of air from the main tank to enter theauxiliary chamber 8. The pressure in the auxiliary tank 8 will increaseand acting through the pipe 7 and hole 23 of the plunger 22 will causethe valves 20 to seat at an earlier point of the suction stroke therebyincreasing the volume offresh air .drawn into the compressor through thein take valve 19 until it equals the increased consumption of compressedair taken from the maintank, the pressure in the tank being slightlyreduced. In case of a decrease in the consumption similar action willtake place and a new equilibrium between supply and consumption will beestablished after a slight increase of the tank pressure. In case ofcompound or multiple air compressors, each stage has its own regulator.Due to the fact that the diflerent stages of multiple stage aircompressors may operate at diflerent 'cut-ofl s, the present system ofregulation is exceedingly flexible and the generally intricate problemsarising in connection with the regulation of such compressors is easilysolved. ile almost any problem of regulation of air compressors, blowingengines, vacuum pumps, etc., can be solved in applying the abovedisclosed principle,

we think that the above three typical cases will sufiiciently illustratethe methods involved.

What I claim is:

1. In combination with a fluid controlling device, which comprises acylinder, a piston controllably variable yieldingv pressure as tocounteract the action of said closing means and actuate the valves ofsaid set during that stroke of the piston which otherwise would be idlewith respect to the valves of that set at a time governed by theintensity of said pressure. 1 1

3. In combination with a fluid controlling device, which comprises acylinder, a piston and automatic inlet and outlet valves, of meanstending to close said valves and fluid operated means for applying tovalves of one set such controllably variable yielding pressure as tocounteract the action of saidclosing means and actuate the valves ofsaid set during that stroke of the piston which otherwise would be idlewith respect to the valves of that set at a time governed by theintensity of said pressure.

4. In combination with a fluid controlling device, which comprises acylinder, a piston and automatic inlet and outlet valves, of meanstending to close said valves and means comprising an auxiliary pressuretank containing a fluid under pressure and having means connected withsaid valves, whereby the fluid of said tank may apply to valves of oneset such controllably variable yielding pressure as to counteract theaction of said closing means and actuate the valves of said set duringthat stroke of the piston which otherwise would be idle with respect tothe valves of that set'at a time governed by the intensity of saidpressure.

5. In combination with a fluid controlling device, which comprises acylinder, a piston, automatic inlet and outlet valves, of means exposedto the pressure in the outlet pipe for applying to valves of one setsuch controllably variable yielding pressure that they will be actuatedupon that stroke of the piston which otherwise would be idle withrespect to the valves of that set at a time governed by the ,intesity ofthe pressure in said outlet pipe.

6. In combination with a fluid controlling Mid device, which comprises acylinder, a piston, automatic inlet and outlet valves, 'of means,influenced by the speed of the prime mover, for applying to valves ofone set such controllably variable yielding pressure that they will beactuated upon that stroke of the piston which otherwise would be idlewith respect to the valvesof that set at a time governed by the degreeof said speed.

7 In combination with a fluid controlling device, which comprises acylinder, a piston,

automatic inlet and outlet valves, of means,

influenced by the power consumption of said device, for applying tovalves of one setsuch controllably variable yielding pressure that theywill be actuated upon that stroke of the piston which otherwise would beidle with respect to the valves of that set at a time governed by theamount of said power consumption.

8. In a fluid controlling device, the combination of a cylinder, apiston, inlet and outlet valves, and variable controllable means toactuate any or all of the outlet valves during that stroke of the pistonwhich otherwise would be idle with respect to said valves at a timedependent on the control of said means.

9. In a fluid controlling device, the combination of a cylinder, apiston, inlet and outlet valves, and means, exposed to the pressure inthe outlet pipe, to actuate any or all of the outlet valves during thatstroke of the piston which otherwise would be idle with respect to saidvalves at a time governed by the intensity of the pressure in saidoutlet pipe.

10. In a fluid controlling device, the combination of a cylinder, apiston, inlet and outlet valves, and means, influenced by the speed ofsaid device, to actuate any or all of the outlet valves during thatstroke of the piston which otherwise would be idle with respect to saidvalves at a time governed by the degree of said speed.

11. In a fluid controlling device, the combination of a cylinder, apiston, inlet and outlet valves, and means, influenced by the powerconsumption of said device, to actuate any or all of the outlet valvesduring that stroke of the piston which otherwise would be idle, withrespect to said valves at a time governed by the amount of said powerconsumption.

In testimony whereof, I the said OSCAR R. WIKANDER, have hereunto set myhand.

. OSCAR WIKANDER.

Witnesses:

J OHN F. WILL, J. R. KELLER.

